What is the significance of the Mossberg "Shockwave"?

I know that the Mossberg "Shockwave" is a pistol grip pump action shotgun with a very short barrel. It comes in 12 and 20ga. I am not sure I understand the laws and rules surrounding this firearm, especially how it is legal with a 14 inch barrel and a non-stock grip. As I understand it, if you put a stock on the Mossberg Shockwave, you would then have a short-barreled shotgun and would be in violation of the law.<br><br>I am in Canada and we don't have these firearms available. It is a fascinating firearm to say the least. <br><br>What is the advantage of the Mossberg "Shockwave"?